I charge a base fee which includes travel,setup/teardown, the first hour of music, and in some cases (small parties, piano+vox only) a small PA; and then an hourly fee ($50-$100) after that. For $250, you may add on the rental of my two 15" JBL SRX speakers, which includes mixing, cables, and stands. This is recommended for outdoor events, larger banquet rooms, 100+ people, weddings, etc. After that, for an additional $200, I have a dual 18" JBL SRX subwoofer. This subwoofer really balances out the sound and adds a fullness to the music -- it looks and feels like a beast. This is highly recommended for dance parties and audiophiles. I typically ask for a deposit for lock down the date. Discounts can be offered if booking multiple dates.
I typically ask for a phone call to get a feel for what we both want and need out of the event; I want to know what your sound requirements are, what kind of music you're into, how you know your guests, etc. For weddings and personal parties, I want to know if there are certain songs that I can learn on piano to add that special sparkle to your ceremony or event.
My belief is that there is no pursuit more noble than that which makes people dance and have a good time.